The present invention relates to the production of a film, starting from an initial wafer, including a step of implanting atomic species through one of its faces in order to form therein a buried implanted zone at a defined depth, with the film to be produced then being bounded by the implanted face of the wafer and by this implanted zone.
This technique is especially employed for lifting off the film, by carrying out, after the implantation, the following steps (illustrated by FIGS. 1A and 1B):                the wafer 10 is bonded on its implanted face to a receiving substrate 20; and        energy (typically thermal and/or mechanical energy) is supplied so as to detach the film 15 from the implanted zone 12 (this process is known in the art by the term SMART-CUT®).        
The film 15 is then taken off the wafer 10, to be transferred onto the receiving substrate 20 (see FIG. 1B).
Referring to FIGS. 1A and 1B, the faces of the wafer 10 are usually chamfered on the periphery (chamfers 11 and 11′), so that the bonding of the receiving substrate 20 to the wafer 10 takes place mainly only on the surface of the wafer 10 that is not located on the chamfer 11.
Thus, referring to FIGS. 1B and 1C, the film 15 is not exactly taken off the entire surface of the wafer 10, since, after taking-off, the chamfered portion of the film initially bounded by the implanted zone remains attached to the wafer 10, thus forming a ring 14 that surrounds a hollow volume corresponding approximately to the volume of the film 15 that is removed.
In the particular case in which the film 15 is made of crystalline material, strains can then propagate throughout the film 15 and thus have major deleterious consequences.
Furthermore, the receiving substrate 20 may itself have a peripheral chamfer, not necessarily identical to the chamfer 11 of the wafer 10, which may therefore be offset relative to the chamfer 11 so that there is irregular detachment of the film 15 along its edges. The latter effect is also accentuated by the fact that the bonding forces at the bonding interface are of course weaker along the edges than in the central portion. The film 15 taken off therefore has rather irregular edges and internal defects or damage.